Examples of antihypertensive drugs include various neuroleptic drugs having effective actions on the neural-factor-related regulatory system, ACE inhibitors having effective actions on the neurohumoral-factor-related regulatory system, AT receptor antagonists, Ca antagonists associated with the vascular-endothelium-derived-substance-related regulatory system, and hypotensive diuretics associated with the body-fluid-regulatory system in the kidney. Under the present circumstances, however, any pharmaceutical drug used for treatment of hypertension imposes a serious burden on patients, because its side effects cannot be lightly ignored notwithstanding its satisfactory effectiveness is acknowledged.
General therapies for improving the life style such as diet therapy, kinesitherapy, and limitation of alcoholic intake or smoking are applied widely not only to patients having a high normal blood pressure including a mild case, but also to patients suffering from severe hypertension. With growing awareness of the importance of general therapies, improvement of eating habits is becoming especially important. There are a number of foods having an antihypertensive effect. Blood pressure lowering materials derived from foods have so far been searched extensively and a number of effective ingredients have been isolated from them or identified.
It is reported that, of such effective ingredients, chlorogenic acid, caffeic acid, ferulic acid and the like contained in foods such as coffee have an excellent antihypertensive effect (Patent Documents 1 to 3). On the other hand, there is a report indicating that a coffee beverage known to contain a large amount of chlorogenic acids was not recognized to have a clear hypotensive effect and rather increased the blood pressure level (Non-patent Document 1).    Patent Document 1:JP-A-2002-363075    Patent Document 2:JP-A-2002-22062    Patent Document 3:JP-A-2002-53464    Non-patent Document: Eur. J. Clin. Nutr., 53(11), 831(1999)